1. Field of the Invention
This invention relates to a stable bleaching composition and also a detergent composition containing such bleaching composition.
2. Description of the Prior Art
It is known in the art that inorganic peroxide bleaching agents capable of releasing active oxygen in an aqueous solution are used as bleaching agents or bleaching detergents for household or industrial uses.
Among these bleaching agents, sodium perborate has a good storage stability when used as a bleaching agent or in the form incorporated with a detergent and, during storage, it hardly causes decomposition which extinguishes oxygen effective for bleaching.
However, the bleaching effect of sodium perborate cannot be sufficiently exerted if the temperature is less than 60.degree.C., and it fails to exhibit a sufficient effect in Japan where the washing is customarily conducted at low temperatures. Therefore, the development of oxygen type bleaching agents having good solubility and high bleaching activity even at low temperatures has been desired in the art.
It is known that some inorganic salts such as alkali carbonates and alkali phosphates form adducts with hydrogen peroxide and these adducts are superior to sodium perborate with respect to bleaching activity and solubility at low temperatures. However, as is well known in the art, in case such an adduct is incorporated into a powdery detergent or bleaching agent under the weather conditions in the summer in Japan such as a temperature of about 30.degree.C. and a relative humidity of about 80%, the occurrence of decomposition is remarkable and, hence, a sufficient bleaching effect cannot be obtained. Various attempts have heretofore been made to improve the poor storage stability, namely, the fatal defect of inorganic peroxide bleaching agents, and the typical instances of such attempts are as follows:
1. A method comprising adding an inorganic salt known as a stabilizer for a peroxide, such as sodium silicate, magnesium silicate, sodium chloride, sodium sulfate and the like. PA1 2. A method comprising incorporating in a peroxide an organic metal blocking agent of the water-soluble polyaminocarboxylic acid type, such as ethylenediamine tetra-acetate (E.D.T.A.), nitrilotriacetate (N.T.A.) and the like. PA1 3. A method comprising granulating or coating a peroxide with a water-soluble or water-insoluble compound such as paraffin wax, polyethylene glycol, alkanol amide and the like.
According to any of the foregoing methods, however, the decomposition of the peroxide is caused to occur considerably during storage and a sufficient stability cannot be obtained.